Conventionally, there has been proposed to promote mixture of air and fuel in a combustion chamber. For example, there is a proposal for a fuel injection nozzle in which a spiral path is formed between a wall surface of a hollow bore of a nozzle body and a sliding surface of a needle (for example, Patent Document 1). In this proposal, the rotational flow of the fuel passed through the spiral path is accelerated in a fuel retaining portion provided at an end of the nozzle body. The fuel has a velocity in the tangent direction of a single jet hole, and spreads into the combustion chamber to mix the fuel and air.    Patent Document 1: Japanese Patent Application Publication No. 10-141183